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brian period was 3 million； 18 million； 600 million； 794million； or 2。4 billion鈥攐r some other number within that range。 as late as 1910； one of themost respected estimates； by the american george becker； put the earth鈥檚 age at perhaps aslittle as 55 million years。
just when matters seemed most intractably confused； along came another extraordinaryfigure with a novel approach。 he was a bluff and brilliant new zealand farm boy namedernest rutherford； and he produced pretty well irrefutable evidence that the earth was at leastmany hundreds of millions of years old； probably rather more。
remarkably； his evidence was based on alchemy鈥攏atural； spontaneous； scientificallycredible； and wholly non…occult； but alchemy nonetheless。 newton； it turned out； had not beenso wrong after all。 and exactly how that came to be is of course another story。
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7 ELEMENTAL MATTERSCHEMISTRY
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as an earnest and respectable science is often said to date from 1661； whenrobert boyle of oxford published the sceptical chymist 鈥攖he first work to distinguishbetween chemists and alchemists鈥攂ut it was a slow and often erratic transition。 into theeighteenth century scholars could feel oddly fortable in both camps鈥攍ike the germanjohann becher； who produced an unexceptionable work on mineralogy called physicasubterranea ； but who also was certain that； given the right materials； he could make himselfinvisible。
perhaps nothing better typifies the strange and often accidental nature of chemical sciencein its early days than a discovery made by a german named hennig brand in 1675。 brandbecame convinced that gold could somehow be distilled from human urine。 （the similarity ofcolor seems to have been a factor in his conclusion。） he assembled fifty buckets of humanurine； which he kept for months in his cellar。 by various recondite processes； he converted theurine first into a noxious paste and then into a translucent waxy substance。 none of it yieldedgold； of course； but a strange and interesting thing did happen。 after a time； the substancebegan to glow。 moreover； when exposed to air； it often spontaneously burst into flame。
the mercial potential for the stuff鈥攚hich soon became known as phosphorus； fromgreek and latin roots meaning 鈥渓ight bearing鈥濃�攚as not lost on eager businesspeople； but thedifficulties of manufacture made it too costly to exploit。 an ounce of phosphorus retailed forsix guineas鈥攑erhaps five hundred dollars in today鈥檚 money鈥攐r more than gold。
at first； soldiers were called on to provide the raw material； but such an arrangement washardly conducive to industrial…scale production。 in the 1750s a swedish chemist named karl（or carl） scheele devised a way to manufacture phosphorus in bulk without the slop or smellof urine。 it was largely because of this mastery of phosphorus that sweden became； andremains； a leading producer of matches。
scheele was both an extraordinary and extraordinarily luckless fellow。 a poor pharmacistwith little in the way of advanced apparatus； he discovered eight elements鈥攃hlorine； fluorine；manganese； barium； molybdenum； tungsten； nitrogen； and oxygen鈥攁nd got credit for none ofthem。 in every case； his finds were either overlooked or made it into publication aftersomeone else had made the same discovery independently。 he also discovered many usefulpounds； among them ammonia； glycerin； and tannic acid； and was the first to see themercial potential of chlorine as a bleach鈥攁ll breakthroughs that made other peopleextremely wealthy。
scheele鈥檚 one notable shorting was a curious insistence on tasting a little of everythinghe worked with； including such notoriously disagreeable substances as mercury； prussic acid（another of his discoveries）； and hydrocyanic acid鈥攁 pound so famously poisonous that150 years later erwin schr？dinger chose it as his toxin of choice in a famous thoughtexperiment （see page 146）。 scheele鈥檚 rashness eventually caught up with him。 in 1786； agedjust forty…three； he was found dead at his workbench surrounded by an array of toxicchemicals； any one of which could have accounted for the stunned and terminal look on hisface。
were the world just and swedish…speaking； scheele would have enjoyed universal acclaim。
instead credit has tended to lodge with more celebrated chemists； mostly from the english…speaking world。 scheele discovered oxygen in 1772； but for various heartbreakingly plicated reasons could not get his paper published in a timely manner。 instead credit wentto joseph priestley； who discovered the same element independently； but latterly； in thesummer of 1774。 even more remarkable was scheele鈥檚 failure to receive credit for thediscovery of chlorine。 nearly all textbooks still attribute chlorine鈥檚 discovery to humphrydavy； who did indeed find it； but thirty…six years after scheele had。
although chemistry had e a long way in the century that separated newton and boylefrom scheele and priestley and henry cavendish； it still had a long way to go。 right up to theclosing years of the eighteenth century （and in priestley鈥檚 case a little beyond） scientistseverywhere searched for； and sometimes believed they had actually found； things that justweren鈥檛 there： vitiated airs； dephlogisticated marine acids； phloxes； calxes； terraqueousexhalations； and； above all； phlogiston； the substance that was thought to be the active agentin bustion。 somewhere in all this； it was thought； there also resided a mysterious 茅lanvital； the force that brought inanimate objects to life。 no one knew where this ethereal essencelay； but two things seemed probable： that you could enliven it with a jolt of electricity （anotion mary shelley exploited to full effect in her novel frankenstein ） and that it existed insome substances but not others； which is why we ended up with two branches of chemistry：
organic （for those substances that were thought to have it） and inorganic （for those that didnot）。
someone of insight was needed to thrust chemistry into the modern age； and it was thefrench who provided him。 his name was antoine…laurent lavoisier。 born in 1743； lavoisierwas a member of the minor nobility （his father had purch